ICS844003I Datasheet, PDF (10/13 Pages) Integrated Circuit Systems – FEMTOCLOCKS™ CRYSTAL-TO-LVDS FREQUENCY SYNTHESIZER

Integrated
Circuit
Systems, Inc.
PRELIMINARY
ICS844003I
FEMTOCLOCKS™ CRYSTAL-TO-LVDS
FREQUENCY SYNTHESIZER
RECOMMENDATIONS FOR UNUSED INPUT AND OUTPUT PINS
INPUTS:
CRYSTAL INPUT:
For applications not requiring the use of the crystal oscillator
input, both XTAL_IN and XTAL_OUT can be left floating.
Though not required, but for additional protection, a 1kΩ
resistor can be tied from XTAL_IN to ground.
OUTPUTS:
LVDS
All unused LVDS output pairs can be either left floating or
terminated with 100Ω across. If they are left floating, we
recommend that there is no trace attached.
TEST_CLK INPUT:
For applications not requiring the use of the test clock, it can
be left floating. Though not required, but for additional
protection, a 1kΩ resistor can be tied from the TEST_CLK to
ground.
LVCMOS CONTROL PINS:
All control pins have internal pull-ups or pull-downs; additional
resistance is not required but can be added for additional
protection. A 1kΩ resistor can be used.
3.3V LVDS DRIVER TERMINATION
A general LVDS interface is shown in Figure 4. In a 100Ω
differential transmission line environment, LVDS drivers
require a matched load termination of 100Ω across near
the receiver input.
3. 3V
LVDS
R1
100
100 Ohm Differential Transmission Line
3. 3V
+
-
FIGURE 4. TYPICAL LVDS DRIVER TERMINATION
844003AGI
www.icst.com/products/hiperclocks.html
10
REV. B AUGUST 25, 2005